Patients with bipolar disorder (BPD) were once thought to achieve complete inter-episode recovery, particularly with regard to cognitive dysfunction. More recent data suggest a persistent, trait-like pattern of neurocognitive impairments in BPD, even during periods of affective remission. At the group level, the severity of these deficits is 3/4 to 1 full standard deviation below average, which is significantly less severe than deficits noted in schizophrenia (SZ). Recent evidence, however, suggests that the frequency of cognitive impairment in euthymic BPD patients is ~40-60%, with a substantial proportion of patients characterized as cognitively- spared. This contrasts with the relative homogeneity of this phenotype in SZ where > 90% of patients demonstrates significant impairment. A better understanding of the cognitive heterogeneity in BPD, why some patients develop significant cognitive difficulties while others do not, is critical toward optimizing patiets' quality of life. The current proposal aims to determine the clinical and biological predictors of cognitive impairment in 350 patients with BPD using a novel approach. We will empirically test for homogeneous subgroups within the sample based neurocognitive performance and test a cassette of clinical features and biomarkers as potential predictors of impairment. We will also investigate the relationship between neurocognitive functioning and everyday functional capacity in the areas of occupational, social and independent living ability. Data will provide important information on the underlying structure of neurocognition in BPD and its etiology, guiding future efforts to target these disabling symptoms with treatment.